This kind of positioning apparatus is generally arranged in such a manner that a circular engaging hole opened in a surface to be supported of the second block is fitted to a plug projected from a support surface of the first block (refer to Japanese Patent Public Disclosure No. 57-27640, for example).
In the case of the prior art, it is necessary to provide a predetermined fitting gap between the engaging hole and the plug to fit them smoothly to each other. Consequently, the fitting gap reduces the positioning accuracy.
The present invention aims at providing an apparatus capable of positioning easily with a high degree of accuracy.